A novel monolithic mullite microfiltration membrane for oil-in-water emulsion separation

Monolithic ceramic microfiltration membranes made up of an interlocking network of mullite crystals have been developed from low-cost raw materials, consisting of China clay, AlF3·3H2O and Al2O3. The characteristics of the developed membranes have been studied. The membrane made from clay+40 wt% AlF3·3H2O powder mixture with 10 wt% Al2O3 displayed excellent properties, with apparent porosity of 64%, median pore diameter of 0.3 μm, flexural strength of 43 MPa, and pure water permeance of 1031 L/m2 h bar. The membrane also displayed excellent pore connectivity and chemical stability owing to the crosslinked needle-like mullite microstructure. The performance of the mullite microfiltration (MF) membrane in oil-in-water emulsion separation was studied with three test solutions having oil concentrations of 200 mg/L, 500 mg/L and 1000 mg/L. The membrane showed excellent permeate flux of more than 200 L/m2. h at a transmembrane pressure of 2 bar and high oil rejection of more than 96% with all the feed concentrations. The fabrication of the monolithic mullite MF membrane in comparison to the conventional asymmetric ceramic MF membranes is highly economical and can be used as a cost-effective alternative for oil-in-water emulsion separation.